The present invention relates to a processing unit and an image forming apparatus including such a processing unit.
A consumable part used in an electrophotographic image forming apparatus reaches the end of its life for replacement some day with frequency of use. Such occasions include: an occasion at which toner in the container of a toner cartridge to be supplied has run out; an occasion at which a developer used in a processing unit has been deteriorated in durability; and a waste toner container has been filled up with water toner.
In general, an image forming apparatus is configured to detect a consumable part of which the lift has reached its end and prompt the user to replace the consumable part with a new one. One of such configurations is a configuration provided with a new/old detection mechanism for identifying a consumable part as a new one or an old one. A conceivable method of detecting the end of life of a consumable part by such a new/old detection mechanism includes: providing the consumable part with an electrical memory device; and writing information into the memory device. However, such a method raises a problem of an increased running cost because a semiconductor memory device is very expensive and, hence, the consumable part itself becomes expensive.
In view of this problem, an image forming apparatus is disclosed which employs a relatively inexpensive new/old detection mechanism without using any expensive member such as a semiconductor memory device (see Japanese Patent Laid-Open Publication No. 2003-316227).
In maintaining a high image quality, the time to replace a consumable part used in an image forming apparatus, particularly the time to replace a processing unit, is critical. Demands exist for further downsizing of image forming apparatus. With downsizing of such an image forming apparatus, the processing unit for use therein has to be downsized also. Accordingly, the new/old detection mechanism for identifying the processing unit as a new one or an old one has to be downsized also. The new/old detection mechanism described in Japanese Patent Laid-Open Publication No. 2003-316227, however, has a problem that new/old detection mechanism cannot accommodate to the downsizing of the processing unit because of its complicated configuration. Further, upon replacement of the processing unit the image forming apparatus has to correctly identify the replacing processing unit as a new one. With the technique described in Japanese Patent Laid-Open Publication No. 2003-316227, however, an inconvenience occurs such that if the gear of the new/old detection mechanism is rotated by accident during the operation of fitting the processing unit on the image forming apparatus, the processing unit cannot be identified as a new one by the image forming apparatus even though the processing unit is a new one.
In view of the foregoing problems, the present invention intends to provide a processing unit which enables an image forming apparatus to correctly identify the processing unit as a new one or an old one even though the image forming apparatus is downsized.